A vehicle driveshaft is typically and operatively mounted to a transmission assembly and to a differential assembly and, more particularly, transfers the transmission produced torque to the differential, thereby causing the vehicle wheels to be desirably and selectively turned. The driveshaft also dynamically compensates for the change or modification in the distance between the transmission and the differential which occurs as the vehicle is driven. Hence, the driveshaft includes a portion or a member which typically and telescopingly moves along the longitudinal axis of the driveshaft in response to relative movement between the differential and the transmission (e.g., the driveshaft is capable of dynamically modifying its length in response to the movement of the vehicle).
This dynamic length modification is typically achieved by the use of a pair of splined members which are normally manufactured of a relatively heavy material, such as conventional and commercially available iron, and which are respectively and commonly referred to as the "slip yoke" and the "yoke shaft". Particularly, the yoke shaft member is selectively inserted into the slip yoke and is movably coupled to the transmission. The slip yoke is typically coupled to the differential and the respective splines of these members (which are typically broached or "machined" onto the yoke members) intermeshingly cooperate to allow and/or to cause the yoke shaft to rotate the slip yoke in response to the rotation of the transmission, thereby allowing the transmission produced torque to be selectively coupled to the differential by the rotation of the slip yoke. The intermeshed splines also allow the yoke shaft to be movable along the longitudinal axis of the driveshaft, thereby allowing the driveshaft to dynamically compensate for changes in the distance between the transmission and the differential and allowing the driveshaft to desirably operate as the vehicle is driven. While these driveshafts allow for the desired communication of the transmission-produced torque to the differential, they suffer from some drawbacks.
First, the yoke members of these prior driveshafts are normally and rather loosely connected because the respective splines are typically formed on only relatively small or relatively short portions of the respective and relatively heavy yoke members. These relatively short intermeshing splined portions allow the engaged members to undesirably "wobble" as the vehicle is driven and produce undesirable noise and vibrations which are undesirably communicated into the passenger compartment. These relatively short "yoke engagement" portions also cause undesirable "backlash" to occur as the transmission generated torque is transferred to the slip yoke member. Secondly, the relatively heavy yoke members require relatively narrowly formed and narrowly spaced splines which cause the engaged members to experience relatively high stress are loads and which further cause undesirable fatigue and/or failure of the splines and/or of the engaged yoke members. Additionally, the relatively heavy material used to form the yoke members requires the yoke members to have a relatively small diameter to avoid the undesirable addition of weight to the vehicle. These relatively small diameter members further cooperatively provided only a relatively limited or small amount of engaging surface or "working" area between the intermeshing yoke members, thereby further causing relatively high stress and loads to be applied and/or transferred among and between the engaged members. Finally, the engaged yoke members are prone to undesirably "buckle" during and/or as a result of a vehicle accident, thereby undesirably damaging many of the vehicle underbody components, including but not limited to, the vehicle fuel tank.
There is therefore a need for (a new and improved vehicle driveshaft which overcomes many, if not all, of the previously delineated drawbacks of such prior vehicle driveshafts.